1. Field of the Invention
This application is filed under 35 U.S.C. 371 and based on PCT/EP98/04208, filed Jul. 7, 1998.
This invention relates to a device for storing, transporting and expressing free-flowing compositions, more particularly adhesives and sealants.
2. Discussion of Related Art
Whenever free-flowing compositions--whether of low or high viscosity--are to be stored or transported for a certain time, they have to be protected against flowing out, drying out or, in the case of reactive compositions (for example sealants and adhesives), against reacting out. Accordingly, the containers accommodating the free-flowing composition are closed and are only opened immediately before use. Opening generally involves a completely separate step. If the container filled with the reaction substance is part of a complex application system, opening of the container at the beginning of dosing is often a complicated step and mistakes can often be made.
In the case of reactive systems, such as adhesives and/or sealants for example, two or more components often have to be separately stored. The separate components are only supposed to come into contact with one another immediately before use and to be thoroughly mixed before they can be applied and react out. For the industrial-scale application of such two-component or multicomponent adhesives and/or sealants or coating materials, this problem has been solved by the installation of generally very expensive dosing and mixing systems. These systems generally enable the two-component or multicomponent compositions to be reliably and properly stored, dosed and correctly mixed.
In the small-user field, i.e. in small-scale production or, more particularly, in the hand-made field or among end users, the dosing and mixing systems referred to above are out of the question for the application of two-component and/or multicomponent compositions because they are too complicated and too expensive. Accordingly, users in these categories generally prefer one-component systems because they can be used with simple applicators without any risk of mixing or dosing errors that could adversely affect the end properties of the bond or seal or coating. In many cases, however, the reaction rate of one-component compositions is not sufficient to develop ultimate strength or a minimum strength so that conventional two-component compositions are still used in cases such these. Since, as mentioned above, elaborate mixing and dosing systems cannot be used here, other approaches have been adopted to reduce the effects of possible mixing errors. In these conventional two-component and multicomponent compositions, the two components generally have equally large volumes and viscosities. However, this means that special two-component application systems are still needed for such two-component compositions. Examples of such two-component systems are coaxial cartridges surmounted by a static mixer of the type marketed, for example, under the name of "Supermix" by Liquid Control. In addition, two-component systems with two parallel cartridges and a dynamic mixing head are known, for example, from EP-B-313 519 and EP-B-351358. DE-A-4202591 describes a process for premixing at least two pastes before introduction into a mixer in which the strands of paste delivered to the mixer form thin adjoining layers. DE-C-2927584 describes an arrangement for dosing two-component products in a predetermined mixing ratio using a piston-and-cylinder assembly in which two cylinders are arranged axially one behind the other. By means of a special mechanism, the two pistons situated between the two chambers can be simultaneously displaced in opposite directions, the component from the rear chamber being guided through a component line leading centrally through the pistons and the front chamber to the front end where a mixing unit is arranged. All these two-component systems require special devices or applicators for their use.
In practice, it is desirable to be able to apply such multicomponent compositions by standard application systems. WO 95/24556 describes a dosing attachment for a cartridge designed to be emptied by means of a press. This dosing attachment contains a mixing component and a dosing chamber with a gear pump driven by two rotors. The main component is accommodated in the cartridge and, when it is squeezed out, drives the gear pump via the rotors so that, with this dosing attachment, at least two components can be mixed together in dosed form by means of a standard cartridge press. The disadvantage of this arrangement is that the dosing attachment contains mechanically moved parts and, in addition, the reactive components are combined in the mixing chamber itself by means of the gear pump so that reactive systems continue to react in the dosing chamber in the event of operational interruptions. This gives rise to serious problems through hardening when work is resumed.
WO 95/127558 describes a process and an arrangement for combining at least two flowable media. In a preferred embodiment, the first (main) medium is accommodated in a standard cartridge. The second chamber containing the second flowable medium is accommodated in an attachment designed to be fitted to the cartridge. This chamber communicates with the flow region and/or with the first chamber through at least one opening element for branching off part of the first flowable medium from the first chamber into the second chamber. The second chamber contains a displaceable separating element which separates the first medium from the second medium and which is moved in the common opening direction by the first medium entering the second chamber so that the second flowable medium is pressed out from the chamber accommodated in the attachment. Although this arrangement gives useful results in many cases, it has been found in practice that serious leakage problems can occur at the inlet and outlet openings, particularly in the case of low-viscosity second media. These are major disadvantages, particularly in the event of prolonged storage of reactive systems and in the event of brief interruptions in application.
Accordingly, the problem addressed by the present invention was to provide a device for expressing flowable compositions which would only release the flow of at least one component under the effect of the expressing pressure applied thereto. More particularly, the problem addressed by the invention was to provide a device for the spatially separate and synchronous expression of two or more free-flowing components, more particularly sealants and adhesives. Preferably, these devices would be able to be used with conventional, widely marketed applicators for one-component adhesives/sealants.